1. Field of the Invention
This invention relates to methods for controlling the delamination within contoured laminated structures and to the structures for carrying out such methods, and more particularly to such methods and structures for limiting or preventing delamination within laminated structures comprising at least one facing laminate and a plurality of spaced ribs attached thereto, and that is either adapted to be configured into a curved shape, thereby maintaining a desired appearance of the laminated structure, or remains in a flat, non-distorted condition to be used to cover a flat surface area.
2. Related Art
The development and subsequent proliferation of high impact decorative surface materials has prompted many changes in the cabinet and architectural industry. These changes included new adhesives, tools, fasteners and assembly techniques. The substrate cores of choice for lamination are composition board for flat panels and papers or plywood for contours.
In most cases, the flat, average size panels are easy to laminate, handle and assemble and are relatively stable. This is not the case when using large panels, contours or closed loop designs. Although many decorative surface materials are durable and flexible, most fabricators are reluctant to produce contoured structures because rigid contoured components are not compatible with flat-line production systems and require special hands-on labor, intensive handling, laminating and assembly methods.
An additional deterrent to the use of such panel structures is that all of the wood base cores expand and contract in response to the atmosphere at different rates of movement than the surface sheet. This dynamic tension is potentially damaging to the surface sheet and glue line or both.
Laminated strips, including at least an outer surface strip having scuff-resistance characteristics, for example, and a desired eye appeal, and a core material, are formed over partially or fully curved structural surfaces such as columns, pillars, kitchen counters, etc., and permanently retained by the use of an adhesive between the inner surface of the laminated strip and the structural surface. The deformation of the laminated strip to form the desired contour shape produces stresses and strains tending to distort the laminated strip, separating it from the structural surface--a process called leveraged delamination. These forces and stresses are primarily caused by a lever and fulcrum action resulting from the bending of the laminated strip to conform to the structural surface, although changes in temperature and humidity are also contributing factors in the build-up of structural stress. Such delamination degrades the surface appearance of the laminated strip and may even adversely affect the adhesion of the laminated strip to the structural surface depending on the severity of the forces causing the delamination. The forces and stresses causing delamination increase with the degree of bending of the laminated strip to conform it to the shape of the structural surface.
The phenomena of delamination is determined by parameters such as the strength of the adhesive, the laminated strip and the structural surface. If the laminated strip is weaker than the adhesive, for example, the laminated strip will distort or tear before delamination occurs. However, if the adhesive is weak, then delamination will occur before distortion or tearing of the laminated strip. It is thus obviously desirable to design the laminated strip and select the adhesive to provide a controlled delamination of the laminated strip to prevent distortion or damage thereto.
U.S. Pat. No. 5,232,762, issued to the same inventor as the subject application, relates to a structural element for initial, substantially flat attachment to the surfaces of high impact sheet materials, and adapted for attachment to curved surfaces and includes a first resilient, semi-flexible, sheet material having a given length and width; a second, flexible sheet material of substantially the same width as the first sheet material; a plurality of parallely-spaced, independent preformed rib members sandwiched between the first and second sheet material and each rib member extending substantially across the width of the first and second sheet material and fixedly attached to both the first and second sheet material by an adhesive with the first and second sheet material being flat, the width and height of the preformed rib members and the distance between adjacent rib members determining the limit of bending of the first or second sheet material; and at least one of the first and second sheet material being shearable, thereby enabling areas and the degree of bending within the areas of the first and second sheet material to be determined by the selective cutting of only the at least one sheet in the spaces formed between the plurality of rib members. In an alternative embodiment only one sheet of flexible material is used and the bending of the structural element is determined solely by the spacing between the rib members and their height and width.
U.S. Pat. No. 4,536,427 relates to laminated contoured structures in which the yieldability of the adhesive material between a facing sheet and the core material enables "contouring" of the laminated structure. The adhesive used remains pliable or toffee-like to allow the necessary separation between the scrim and the core.
U.S. Pat.No. 3,540,967 discloses contour-core structures in which the adhesive material between a scrim and the core is dislodged to enable the structure to conform to a curved-shape surface.
Controlling the properties of the adhesive is also an important factor in preventing "telegraphing" or the creation of flex lines or cracking in the laminated strip. Too strong an adhesive preventing delamination results in such cracking or the creation of flux lines in the outer surface of the laminated strip.
Thus, it is desirable to control the delamination of the adhesive from the structural surface and/or control the delamination of the laminated structure from the adhesive in order to prevent the aforementioned problems from occurring. As is evident from the above discussion, prior attempts to achieve controlled delamination rely entirely on the selection of a proper adhesive. Very little consideration has been given to the flexibility of the laminated strip itself in controlling the delamination of the laminated strip from the structural surface.